Many portable electronic devices are powered by a rechargeable battery. A rechargeable battery consists of one or more rechargeable electrochemical cells. The type of chemical comprising the cells--for example, Nickel Cadmium (NiCd), Nickel Metal Hydride (NiMH), and Lithium Ion establishes the battery type.
Although different battery types exhibit different electrical characteristics, they are often used interchangeably to power portable electronic devices. This can create difficulties because different types require different charging schemes. For example, NiCd and NiMH batteries are most effectively charged by a charging current that is applied at a fast rate. A lithium battery can be charged at a fast rate, but this must be done according to a specific profile of current and voltage. These profiles require variations in charging current between the fast slow rates and, thereby, add to the overall complexity of the charging scheme. Accordingly, to provide the appropriate charging current, a charger must know the type of the battery to be charged.
To accommodate these different battery types, existing chargers identify the battery type in various ways. One way is to equip different battery types with resistors having different resistance values. The charger senses the voltage across the resistor of the battery and determines the battery type by comparing the sensed voltage to voltages and associated battery types contained in a look-up table read from the charger's memory.
The battery type is determined upon direct attachment of the battery to the charger. However, if the battery does not fit in the charger, the charger cannot charge the battery. This dependency on the intermating ability of the battery and charger is eliminated by providing a charger that connects directly to the portable electronic device to charge a battery attached to the device. However, with this connection, the existing charger cannot read the battery type from the battery.
What is needed is an improved apparatus and method for battery type identification.